1. Field of the Invention
This invention relates to container closures and more particularly to a plastic bottle cap.
2. Description of the Prior Art
Molded plastic bottle caps for containers having projecting necks are well known. Further, tamper proof or tamper indicating bottle closures have also been well known. Recently, a new style of plastic cap having a axial end wall with circumferentially inner and circumferentially outer portions with the circumferentially inner portion connected to the circumferentially outer portion through a downwardly projecting convoluted band has been proposed. The inner portion has two stable positions, one projecting considerably above the circumferentially outer portion and the second stable position having the top of the central portion lying substantially on a plane with the circumferentially outer portion. The cap is installed on the bottle with the inner portion initially in the raised position and the convolution band extending downwardly into the neck of the bottle from the circumferentially outer portion then reversing itself and projecting outwardly to the raised central portion. Thereafter the central portion is depressed to the position where its axial top is substantially planar with a circumferentially outer portion and the convoluted portion rolls downwardly into the bottle to accommodate the change in height of the inner portion. Such caps are shown, for example, in U.S. Pat. No. 4,341,320 issued July 27, 1982, to Sideny M. Libit, the teachings of which are herein specifically incorporated by reference.
Such bottle caps have the practical benefit of being able to indicate when the bottle has been opened subsequent to packaging. Since an attempt to replace the cap on the bottle will cause the convoluted band to engage the axial end of the bottle neck, further attempts to screw the cap onto the bottle neck will cause the central portion to resume its raised position. While such caps are therefore an important advance over prior art non-tamper indicating caps as well as many types of prior art tamper indicating caps, they have a disadvantage in that due to the initial downward projection of the convoluted portion they may be somewhat more difficult to attach to the neck by automated capping machines due to the absolute necessity of aligning the bottle neck between the skirt and the convolution band so that the skirt is aligned with the o.d. of the bottle neck and the convolution band aligned with the i.d. of the bottle neck. If the gap between the skirt and the o.d. of the convolution band is greater than the thickness of the bottle neck material, then a gap could occur between the bottle neck i.d. and the convolution band o.d. which gap could adversely effect sealing. Since bottle necks, particularly molded or blown plastic bottles do not normally have precise neck inner diameter surfaces, due to the inherent nature of the blow molding process, such prior art caps where the convolution band initially projects into the interior of the bottle neck may have disadvantages.
It would therefore be an advance in the art to provide an improved plastic bottle closure having the advantages of tamper indication disclosed in the aforementioned prior art while avoiding the defficiencies of that prior art caused by the use of the convolution band.